Purpose of review: To highlight the human studies published over the past year examining the influence of vitamin D on risk of colorectal cancer.
Recent findings: Studies over the past year have added more support to the idea that higher levels of vitamin D may decrease risk of colorectal cancer. Further, typical dietary intakes such as 200-400 IU/day may be too low to exert appreciable benefits, and protection may occur with higher levels of vitamin D associated with exposure to sunshine. Recent studies also suggest a potential benefit of vitamin D on other digestive-tract cancers, and that vitamin D status at the time of diagnosis and treatment may influence survival of cancer. However, the evidence for these latter findings is based on limited data and needs to be confirmed. Higher vitamin D levels may also be associated with a higher rate of apoptosis in colorectal mucosa.
Summary: Recent studies add more support to a potential role of vitamin D on risk of colorectal cancer, but suggest that intakes higher than customary are required if solar ultraviolet-B exposure is low. More studies are required to determine the optimal levels and intakes of this vitamin to reduce cancer risk. Potential benefits of vitamin D on other digestive-tract cancers and on survival in patients with colorectal cancer have been suggested by recent studies, but require confirmation.